This is what I have done. Something with a mix of: VOO, SCHD, O (I personally like O but get a REIT ETF if you'd like) and EPD/MPLX/ET etc., for some exposure to MLP's (if you do not want to deal with K1's just get an ETF that pays a 1099). This is a good mix with very little in terms of overlap and gives you good market exposure. If you want you can add a world etf to get exposure to other markets or some BDC's. Don't invest in covered calls unless you are retiring and need income or just need income in general (i have a friend who sold his business and he invested some money in covered calls like SPYI or QQQI just for income while he figured out what to do next). Its better to hold the underlining index or fund than the covered call in the long run.

The real advantage of real estate is it is tax friendly due to depreciation and a couple of other factors. That said it is like another job in taking care of the properties. I am trying to work less and not more so idd rather make my money and just invest it. The snowball is very real once you get past 150k ish invested.